Final answer:
To estimate the platelet count per microliter (µL) of blood based on a microscopic count from a blood film, the correct multiplier is 20,000. This factor accounts for the area surveyed on the blood film and the dilution factor used during the preparation of the sample.
Step-by-step explanation:
To estimate the concentration of platelets per microliter of blood, we often use a blood film and a multiplication factor that corresponds to the dilution made during the preparation of the sample. For example, in microbiology, if 50 colonies are counted on a dilution of 1:10,000, and only 0.1 mL is plated, the multiplier to reach the original concentration would be 10 × 10,000. Analogously, for platelet estimation, if we observe a certain number of platelets within a defined area of a blood smear (using a specific magnification), we use the appropriate factor to extrapolate this count to the number of platelets per microliter (µL) of blood.
The typical number of platelets present in the blood ranges from 150,000 to 400,000 per microliter, and the standard practice for estimation involves multiplying the observed count by 20,000 to obtain the estimate of platelets per microliter of blood. Therefore, the correct multiplier to use in the given question is 20,000.
To estimate the platelet count per microliter (µL) of blood from the blood film estimate, multiply the observed count by 20,000. This factor accounts for the area surveyed and the expected concentration range of platelets in normal blood plasma.